Insurance News

Lightning inside hurricane could predict intensity

Posted on: July 31, 2009

LOS ALAMOS, N.M. – They’re deceptively simple-looking detectors: one an antenna with built-in GPS, the other electronic sensors inside a large, upside-down metal salad bowl.

The sensors are the basis of a Los Alamos National Laboratory project studying lightning inside a hurricane to improve the accuracy and timeliness of forecasts for people in a storm’s path.

The effort is in the second of three years of research. The team is gearing up for the Atlantic hurricane season that peaks in August and September.

Hurricane watchers use satellite images and computer simulations to forecast a storm’s trajectory, but it’s a challenge to predict how a hurricane will strengthen or weaken as it approaches land, lightning and radio scientist Xuan-Min Shao said.

Predictions of where a hurricane will hit have improved by 50 percent in the past two decades, said Robert Atlas, director of the National Oceanic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory near Miami.

But, he said, NOAA and its partners have not made the same leap in forecasting storm strength, “largely because you’re dealing with … what’s going on within the hurricane itself.”

After research, the next step would be an operational system. Los Alamos, as a federal research laboratory, is not in the business of producing forecasts.

“The National Weather Service does that,” said Chris Jeffery, one of the project’s scientists. “This is a research and development project to demonstrate new technology, understand new fundamental relationships.”

Their project spun off from the lab’s work in nuclear nonproliferation.

Scientists trying to ensure that countries are not secretly detonating nuclear weapons must know the difference between radio signals produced by a nuclear bomb and anything else lightning, for example.

Lightning and nuclear bombs both release radio waves at different frequencies.

The team, which has not published its research, found a close correlation between lightning and hurricane intensification in a study of nonproliferation sensor data gathered in 2005 during Hurricanes Katrina and Rita.

“If your hurricane people see the lightning all of a sudden become very active, you are probably expecting in the next couple hours that this hurricane will be intensified,” Shao said.

Finding lightning associated with a hurricane eyewall the wall surrounding the eye of the storm is not new. But the Los Alamos scientists said their data was gathered from greater distances and tracked not only lightning bolts hitting the ground, but also flashes within clouds.

The intensity of intercloud flashes can help determine such things as the height of the storm, which researchers said can help determine whether the eyewall is symmetrical and tight.

The structure is important because a towering eyewall puts a lot of energy into the storm, Jeffery said.

“Eventually that energy works its way up and if your conditions are right, it forms a symmetric tight eyewall. It will spin up the storm,” he said.

Jeffery is the principal investigator in the Hurricane Lightning Project, which involves densely packing sensors around the New Orleans area to observe hurricanes at a far higher resolution than possible in the past.

Scientist Cheng Ho heads a related project, the Los Alamos Sferic Array, which has stations in Florida and along the Texas coast operating at a low-frequency band that can detect storms thousands of miles away. The two complementary arrays cover the entire U.S. Gulf Coast.

“So if we’re lucky we’ll get a reasonable size, but not very damaging, hurricane hitting the New Orleans area, so we get the data but not much damage,” Ho said. “If somehow the hurricane goes the other direction, then this wider arm will catch it.”

Shao said the dual-band observations will not only pinpoint the location of lightning for researchers but also the physics involved by producing a three-dimensional picture.

The project needs multiple sensors to get a reading on the electromagnetic pulse produced by lightning.

“We can compare all the signals from the different stations and triangulate where the signal comes from,” Shao said.

All the data gathered during a hurricane is sent over the Internet to Los Alamos for the team to analyze. The GPS provides accurate time information from the electromagnetic signals.

Pointing to a shelf with a line of retired sensors in inverted salad bowls from the local supermarket, Shao joked, “These are Mach zero salad bowls and we are going to Mach 4 salad bowls.”

Atlas said new insights eventually could translate into improved forecasts up to one week before a hurricane hits land crucial because of the time needed to evacuate a growing population along the coast.

“We believe if we do this, public confidence in the forecasts and public adherence to warnings will be dramatically increased so lives will be saved,” he said.

Copyright © 2009 The Houston Chronicle

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